1. Field of the Invention
The present invention relates generally to methods and apparatus for imprinting images on the surfaces of three-dimensional objects. More particularly, the invention concerns a novel, improved method and apparatus for non-contact, high-quality, distortion-free printing of images on non-planar surfaces of three-dimensional objects using ink jet printing technology.
2. Discussion of the Prior Art
Various types of image transfer techniques have been suggested in the past for imprinting images on a number of different material surfaces including cloth, wood, metal and ceramics. A very common technique, which has been widely used, is silk screening. However, such a technique is generally limited to printing on smooth, flat surfaces. Further, such technique produces a relatively low quality print when compared to that produced by lithography, gravure, letterpress sublimation and laser printing.
When the image is to be transferred to a metal surface, prior art sublimation techniques are frequently used. For example, Blake, et al., U.S. Pat. No. 3,484,342 issued Dec. 16, 1969 and Fromson, et al., U.S. Pat. No. 4,201,821 issued May 6, 1980 both suggest decorating unsealed and coated anodized aluminum using sublimation techniques. However, sublimation processes also have substantial drawbacks, particularly when the surface of the object, which is to be printed, is non-planar.
When printing on non-planar surfaces is required, several techniques have been suggested. For example, U.S. Pat. No. 4,741,288 issued to Stirbis, et al., discloses an apparatus for decorating a cylindrical can. The Stirbis, et al., apparatus makes use of a multiple station ink supply and a transfer apparatus for transferring ink from an ink fountain to a rotatable inking blanket wheel through a plate cylinder. The apparatus includes an ink image registration adjustment apparatus and an axial and circumferential tightness control apparatus operatively associated with each plate cylinder and each ink supply and transfer apparatus. In addition to techniques involving the use of rotatable inking wheels such as described in Stirbis, et al., other techniques, which have been suggested for imprinting images on non-planar surfaces, include electrophotographic imaging and magnetic imaging. As a general rule, these techniques have met with limited commercial success.
U.S. Letters Pat. No. 5,831,641 issued to Carlson discloses a method and apparatus for imprinting images on non-planar surfaces, including the surfaces of various types of three-dimensional articles, such as baseball bats. The apparatus includes a modified ink jet plotter coupled with an article-positioning apparatus which functions to automatically maintain the surface of the article to be printed within a plane substantially parallel to and slightly spaced-apart from the place within which the ink jet nozzles of the ink jet plotter reside.
Another prior art technique, which is frequently used to decorate surfaces, such as anodized aluminum surfaces, involves the use of transfer films. These films typically overlay the metal surface and, undesirably, are subject to film deterioration and unattractive abrasion. A very popular prior art printing technique, which has found wide acceptance in recent years, is ink jet printing. Within perhaps the last five years this technology has become the dominant technology for printing color images and graphics in the office and home markets. Ink jet printing basically involves a process whereby ink particles are projected in a continuous stream toward the surface to be imprinted using appropriate computer control to create text and graphics on the printing substrate. A number of different types of ink jet printers/plotters are readily commercially available from sources such as Calcomp, Packard Bell, NEC Technologies and Mutoh America, Inc.
By way of brief explanation of the prior art, traditional ink jet printing processes or methods applied to either planar or non-planar objects, typically utilize left to right jetting initially and on the return, jetting right to left. Upon completion of a dual, one line horizontal print, the object is indexed or advanced approximately 1/64 inch, so that the next line can be bi-directionally jetted. This method of printing takes considerable time when high quality multi-colored photo realistic images, text and graphics are required. The only practical way of increasing speed in this type of bi-directional printing is to add a multiplicity of ink jet-heads in parallel and stack them vertically, thus increasing cost and increasing the amount of maintenance required to achieve a consistent quality print over time.
As will be better understood from the discussion which follows, the method and apparatus of the present invention overcomes most of the problems encountered in prior art attempts to print detailed images on non-planar surfaces by employing a highly novel ink jet image transfer technique.